Description Coloration is highly variable, commonly dark brown to black or blue dorsally fading to a dull white ventrally. Dorsal fin may flop to one side when above the surface. Short, rounded snout, cavernous jaw, up to 1 meter (3 ft 3 in) in width, long and obvious gill slits that nearly encircle the head accompanied by well-developed gill rakers, small eyes, and small average girth. Often noticeably scarred, possibly through encounters with lampreys or cookiecutter sharks.

Discussion The basking shark is a passive filter feeder, filtering zooplankton, small fish and invertebrates from up to 2,000 short tons (1,800 t) of water per hour. They feed at or close to the surface with their mouths wide open and gill rakers erect. Unlike the megamouth shark and whale shark, the basking shark does not appear to actively seek quarry, but it does possess large olfactory bulbs that may guide it. It relies only on the water that it pushes through its gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills.

The basking shark's liver, which may account for 25% of its body weight, runs the entire length of the abdominal cavity and is thought to play a role in buoyancy regulation and long-term energy storage.